Improvements in or relating to glasses with selectively adjustable optical power lenses

ABSTRACT

A method of fabricating a lens element for an adjustable power lens of the kind comprising two lens elements that are slidable relative to one other in a direction transverse the optical axis of the lens and have respective lens surfaces that are shaped to act together to form a corrective lens, the power of which varies according to the relative disposition of the two lens elements, the method comprising the steps of forming a lens puck having two opposite faces, which are shaped to form opposite lens surfaces of one of the lens elements of the adjustable power lens, the puck having at least one alignment feature, and thereafter edging the puck to a desired eye shape with reference to the alignment feature.

The present invention relates to glasses with selectively adjustableoptical power lenses and has particular reference to glasses in which atleast one of the lenses comprises two superposed lens elements and aselectively operable optical power adjuster, the lens elements beingslidable relative to each other in a direction transverse the opticalaxis of the lens under the control of the optical power adjuster andhaving respective lens surfaces that are shaped to act together to forma corrective lens, the power of which varies according to the relativedisposition of the two lens elements.

Variable power lenses comprising two lens elements arranged in tandem,one behind the other along the optical axis of the lens, are disclosedin U.S. Pat. No. 3,305,294 (Alvarez), the contents of which areincorporated herein by reference. According to U.S. Pat. No. 3,305,294,each of the lens elements has polished surfaces, with one of thesurfaces being a regular surface of revolution, and an optical thicknessvariation parallel to the optical axis less than one-half the lensdiameter, the optical thickness t of each lens element parallel to theoptical axis z being substantially defined by the formula:

$\begin{matrix}{t = {{A\left( {\frac{x^{3}}{3} + {xy}^{2}} \right)} + {Dx} + E}} & (I)\end{matrix}$

wherein D is a constant representing the coefficient of a prism removedto minimise lens thickness and may be zero, E is a constant representinglens thickness at the optical axis, x and y represent coordinates on arectangular coordinate system centred on the optical axis and lying in aplane perpendicular thereto, t is the optical thickness parallel to theoptical axis and A is a constant representing the rate of lens powervariation with lens movement in the x direction. It will be understoodthat the direction of movement in the x direction is positive for onelens element negative for the other lens element.

Spectacles incorporating such variable power lenses are disclosed inU.S. Pat. No. 5,644,374 (Mukaiyama et al.), United States patentapplication publication no. US 2008/0030678 A1 (Koops et al.), UnitedStates patent application publication no. US 2009/0122254 A1 (Van derHeijde et al.) and international patent application publication no. WO2013/030603 A1 (Gici Labs LLP).

It is an object of the present invention to provide an improved pair ofglasses comprising at least one selectively adjustable optical powerlens of this kind.

A different aspect of the invention provides an improved method ofmaking adjustable lenses and lens elements for incorporation into suchadjustable lenses.

According to a first aspect of the present invention there is providedpair of glasses comprising two lenses and one or more frame parts;wherein one or both of the lenses is adjustable, comprising twosuperposed lens elements and a selectively operable optical poweradjuster, the lens elements being slidable relative to each another in adirection transverse the optical axis of the lens under the control ofthe optical power adjuster and having respective lens surfaces that areshaped to act together to form a corrective lens, the power of whichvaries according to the relative disposition of the two lens elements;wherein the lens elements are configured and arranged such that uponincreasing the optical power of the adjustable lens, the centrationdistance between the two lenses progressively decreases.

Generally, in all of the various aspects of the present invention, theone or more frame parts may themselves be adapted for supporting theglasses on a user's face. In some embodiments, for example, the frameparts may comprise temple arms (or “temples”). However, in otherembodiments the frame parts may be mounted to a head-band, a helmet,goggles or any other equipment or part for holding the frame parts, withthe lenses, in front of the user's eyes.

The or each adjustable lens defines an optical axis and its two lenselements are superposed one behind the other along the optical axis ofthe lens. The one or more frame parts typically comprise a nose-bridge,and suitably the lens elements are configured and arranged such thatupon increasing the optical power of the adjustable lens, the mid-pointof the two lens elements moves towards the nose-bridge. The or eachadjustable lens may have an axis of relative movement between the lenselements that extends generally towards and away from the nose-bridge.When worn, the axis of relative movement may be oriented generallyhorizontally. Adopting the same coordinate system of mutuallyperpendicular axes x, y and z as described above in relation to formula(I) to define parameters of the lens, the optical axis of the lens maybe taken to be the z axis, the axis of relative movement of the lenselements may be designated the x axis, while they axis may be designatedperpendicular to the x axis and perpendicular to the optical axis z.When the glasses are worn, they axis will usually be oriented generallyvertically.

In a pair of glasses, the centration distance between the two lensesshould substantially match the interpupillary distance of the user'seyes. When viewing a near object, the user's eyes converge, such thatthe interpupillary distance (“near PD”) is shorter than theinterpupillary distance when viewing a distant object (“distant PD”). Inaccordance with the first aspect of the present invention, the twosuperposed lens elements of the one or more adjustable optical powerlenses are advantageously configured and arranged such as the opticalpower of the lens is increased for viewing near objects (e.g., forreading) the centration distance of the glasses is progressivelyreduced.

Since the lens elements of the at least one adjustable lens are movablerelative to one another, at least one of the lens elements will usuallyhave a periphery that is at least partially visible within the field ofvision of the user when the glasses are worn. The visible portions ofthe periphery of the at least one lens element may be visible as anedge. In some embodiments, both lens elements may have a periphery thatis at least partially visible as an edge to the wearer. Alternatively,one of the lens elements may have periphery that is visible at least inpart, while the other lens element may have a periphery that isconcealed by one or more of the frame parts such, for example, as a rimor surround, which serves to hide at least part of the edge of the otherlens element.

If the lens elements are movable relative to one another along thex-axis, as described above, at least portions of the periphery of the atleast one lens element that extend along the y-axis may be visible tothe user. In particular, an inner side edge disposed proximate thenose-bridge and an outer side edge disposed away from the nose-bridgemay be visible as edges, as described above. By configuring andarranging the lens elements of the at least one adjustable lens suchthat as the optical power of the lens is increased by moving the lenselements relative to one another along the x-axis such that thecentration distance between the two lenses of the power of glasses isdecreased, the inner side edge of the at least one lens element may moveprogressively towards the nose-bridge. In this way, as the wearerincreases the power of the at least one adjustable lens for viewing nearobjects, and the user's eyes converge, the visible edge at the innerside of the at least one lens element is moved towards the nose-bridgeto offer minimal distraction to the wearer.

In some embodiments, the two superposed lens elements may be arrangedsuch that when they are arranged in the position of maximal opticalpower, the inner or outer side edges of the two lens elements may besubstantially aligned with one another, one behind the other. In someembodiments, in the maximal power position, the inner side edges of thelens elements are substantially aligned with one another.

The lens elements may have different widths between their respectiveinner and outer side edges. One of the lens elements may be narrowerthan the other in the direction of relative movement of the lenselements, i.e. along the x-axis. Suitably the difference in the widthsof the two lens elements along the x-axis should be no more than about 8mm, preferably less than about 6 mm and more preferably no more thanabout 4 mm.

Each of the lens elements may have an inner side edge and an outer sideedge. When the at least one adjustable lens is arranged in its positionof maximal power, the inner side edges of the two lens elements may besubstantially aligned while their outer side edges may be spaced fromone another along the x-axis, for example by a distance equal to thedifference in the widths of the two lens elements, as mentioned above.

When the lens is arranged in its position of minimal power the inner orouter side edges of the two lens elements may be substantially alignedwith one another in the direction of the optical axis. In someembodiments, in the minimal power position, the outer side edges of thelens elements may be substantially aligned with one another, while theirinner side edges may be separated by a distance equal to the differencein the widths of the two lens elements along the x-axis.

The surfaces of the lens elements should be shaped to provide therequired change of optical power between the minimal and maximal powerpositions.

In some embodiments, both lens elements of the at least one adjustablelens may be movable relative to the one or more frame parts, providedthat they are configured and arranged as described above, butconveniently the lens elements may be mounted to the one or more frameparts such that one of the lens elements is movable and the other lenselement is immovable relative to the one or more frame parts. Typically,the glasses will have a front and a back relative to the user when theglasses are worn. For aesthetic and practical reasons, the immovablelens element may be mounted in front of the movable lens element. Bymounting the movable lens element behind the immovable lens element, themovable lens element may be better protected when the glasses are used.When viewed from the front, the immovable element part may present amore attractive, “normal looking” appearance for the lens than would bethe case if the movable lens element were positioned at the front.

The movable lens element may comprise a transparent lens element that ismounted slidably to a frame body for sliding movement in a directiontransverse the optical axis of the lens, i.e. the x-axis. The immovablelens element may comprise a transparent lens element that is mounted tothe frame body or another frame part such, for example, as a surround.

In some embodiments, the immovable element part may comprise atransparent lens element that is mounted to a detachable frame part,such as a surround, that can be removably fastened to the frame body. Asdescribed below, this may facilitate cleaning of the at least oneadjustable optical power lens.

Typically, both lenses of the power of glasses in accordance with thefirst aspect of the present invention may be adjustable. The lenses maybe independently adjustable, but in some embodiments the lenses may belinked so they are adjusted together.

In some embodiments, the lens elements may be mounted to the one or moreframe parts such that the one lens element is slidably mounted to aframe body forming part of the one or more frame parts and the otherlens element is mounted to a detachable frame part that is removablyfastened to the frame body, the frame body and the detachable frame partbeing provided with mutually cooperating formations for accuratelypositioning the other lens element relative to the one lens element.

In accordance with a second aspect of the present invention thereforethere is provided a pair of glasses comprising two lenses and one ormore frame parts, including a frame body and one or more detachableframe parts, at least one of the lenses comprising two superposed lenselements and a selectively operable optical power adjuster, the lenselements being slidable relative to each another in a directiontransverse the optical axis of the lens under the control of the opticalpower adjuster and having respective lens surfaces that are shaped toact together to form a corrective lens, the power of which variesaccording to the relative disposition of the two lens elements; whereinthe lens elements are mounted to the one or more frame parts such thatone of the lens elements is slidably mounted to the frame body and theother lens element is mounted to a detachable frame part that isremovably fastened to the frame body, the frame body and the detachableframe part being provided with mutually cooperating formations forlocating the other lens element relative to the one lens element.

Preferably, the other lens element is mounted to the detachable framepart such that it is immovable relative to the detachable frame part.

Suitably the detachable frame part may comprise a peripheral surroundthat carries the other lens element.

By arranging for the detachable frame part to be removably fastened tothe frame body, it can be removed from the frame body when desired forcleaning the lens elements. The at least one adjustable lens defines anoptical axis, and its two lens elements may be superposed one behind theother along the optical axis of the lens. Each lens element may betransparent, having two opposite faces, one of which is disposedinteriorly of the lens, and the other of which is disposed exteriorly ofthe lens. The respective interior lens faces of the two lens elementsare disposed opposite one another along the optical axis. By detachingthe detachable frame part from the frame body, the interior lens facesof the two lens elements may be accessed for cleaning. Suitably, theother lens element may be completely detached from the frame body.

In order to provide a variable power lens, one face of each lens elementis formed with a cubic or higher order lens surface, and the other facemay be formed with a surface that is a regular surface of revolution. Insome embodiments, a cubic or higher order lens surface may be formed onthe interior lens face of each lens element, while the regular surfaceof revolution may be formed on the exterior lens face. The regularsurface of revolution may comprise a sphero-cylindrical surface.Alternatively, the other face of one or both lens elements may be formedwith a multifocal or progressive lens surface. For various optical andergonomic reasons, it may be desirable for the lens to define a basecurve.

Advantageously, the interior faces of the lens elements may be coatedwith a hydrophobic, super-hydrophobic or oleophobic coating to aidkeeping the interior faces clean and free from dust etc. By way ofexample, PTFE or a similar base material of the kind well-known in theophthalmic industry may be used for this purpose.

Any suitable mutually cooperating formations for accurately positioningthe detachable frame part on the frame body when attached may be used,but conveniently the mutually cooperating formations may comprise aplurality of alignment pins and corresponding recesses. In someembodiments, the mutually cooperating formations may also be used forattaching the detachable frame part to the frame body, for example byway of friction or snap fitting, but in other embodiments the mutuallycooperating formations may be used solely for locating the detachablepart on the frame body, and other means may be provided for releasablyfastening the detachable part to the frame body. For instance, thedetachable frame part and the frame body may be shaped to fit togetherto form a friction fit or snap-fitting. In some embodiments, one or moremagnets may be used to attach the detachable part releasably to theframe body. For instance, one or more magnets may be incorporated intothe frame body, and the detachable frame part may be made at least inpart from a ferromagnetic metal, or vice versa. In some embodiments, oneor more magnets may be embedded in both the frame body and thedetachable part.

In some embodiments, the other lens element may comprise a transparentlens element that is mounted to the detachable frame part, such as asurround as mentioned above. The detachable frame part may be formedwith a plurality of alignment pins and/or recesses that are configuredand arranged to cooperate with a corresponding plurality of recessesand/or alignment pins on the frame body for accurately locating theother lens element relative to the one lens element. It will beunderstood that it is not necessary for all of the alignment pins to beplaced on one or other of the frame body or detachable frame part andall of the recesses to be formed in the detachable frame part or framebody, but it may be convenient to do that in some embodiments.

The pair of glasses will usually inherently define a front and backrelative to the user when worn. For the reasons described in relation tothe first aspect of the present invention, the other immovable lenselement may advantageously be positioned in front of the one slidablelens element.

In accordance with a third aspect of the present invention there isprovided an adjustable power lens assembly comprising one or more frameparts, including a frame body, two superposed lens elements and anoptical power adjuster, the lens elements being slidable relative to oneanother in a direction transverse the optical axis of the lens under thecontrol of the optical power adjuster and comprising respective lenssurfaces that are shaped to act together to form a corrective lens, thepower of which varies according to the relative disposition of the twolens elements; wherein at least one of the lens elements is mountedslidably to the frame body and has a periphery with a plurality of guideformations that cooperate with corresponding formations on the framebody for guiding movement of the at least one lens element relative tothe other lens element; wherein the at least one lens element isspring-loaded against the frame body in a direction orthogonal to theaxis of sliding.

The adjustable power lens assembly defines optical axis and its two lenselements are superposed one behind the other along the optical axis ofthe lens. Adopting the same coordinate system of mutually perpendicularaxes x, y and z as described above to define parameters of the lens, theoptical axis of the lens may be taken to be the z axis, the axis ofrelative movement of the lens elements may be designated the x axis,while they axis may be designated perpendicular to the x axis andperpendicular to the optical axis z. The at least one lens element maybe sprung-loaded against the frame body in a direction orthogonal to theaxis of sliding and the optical axis for registration of the one lenselement to a datum. Suitably, therefore, the at least one lens elementsmay be spring-loaded on the y-axis for registering the lens element tothe datum, thereby accurately positioning the lens element relative tothe frame body in a direction perpendicular to the direction of relativemovement between the two lens elements. In this way, the position of theat least one lens element on the y-axis relative to the frame body maybe accurately controlled. Its position along the x-axis is controlled bythe optical power adjuster. Advantageously, the rotational tolerance ofthe at least one lens element relative to the frame body may beminimised. However, in some embodiments, the at least one lens elementmay additionally or alternatively be sprung-loaded against the framebody in the z-direction.

The at least one lens element may be spring-loaded by at least onespring positioned between a respective one of the guide formations andthe frame body in a corresponding recess formed in the frame body.

In some embodiments, at least one of the guide formations may comprise atab that protrudes from the at least one lens element. The at least onelens element may therefore be spring-loaded by means of at least onespring positioned between the tab and the frame body in thecorresponding recess. Said spring may comprise a compression spring,cantilever or leaf spring, for example.

In some embodiments, at least two of the tabs may be provided thatprotrude outwards from the periphery of the at least one lens element inthe same general direction as each other and are received in one or morecorresponding channels in the frame body, the tabs and one or morechannels being configured and arranged to define a locus of movement ofthe lens element relative to the frame body. The locus of movement mayextend along the x-axis. In some embodiments, the at least two tabs mayprotrude in the direction of the y-axis. The locus of movement may becurvilinear, which is especially suitable for optical lenses having abase curve as described above, for example in a pair of glasses.

At least one other tab may protrude from the periphery of the at onelens element and be received in a corresponding channel formed in theframe body, said other tab being spring-loaded against the frame body inthe direction of the at least two tabs for urging the lens element intopositive alignment with the frame body.

Typically, the lens may have a generally quadrilateral shape, having twoopposite longer sides and two opposite shorter sides, wherein the atleast one lens element is arranged to slide relative to the frame bodyin a direction generally parallel to the longer sides, the at least twotabs being positioned on one of the longer sides, and the other tabbeing positioned on the other longer side.

The channels may be shaped as channels or pockets in the frame body.Alternatively the channels may be formed as a series of formations onthe frame body that serve to guide the guide formations or tabs forguiding movement of the at least one lens element.

In some embodiments, one of the lens elements may be mounted slidably tothe frame body for movement relative to the other lens element, whilethe other lens element may be mounted to the one or more frame partssuch that it is immovable relative to the frame parts.

In a fourth aspect of the present invention there is provided a pair ofglasses comprising at least one adjustable power lens assembly accordingto the third aspect of the invention.

In a fifth aspect of the present invention there is provided a method offabricating a lens element for an adjustable power lens of the kindcomprising two lens elements that are slidable relative to one other ina direction transverse the optical axis of the lens and have respectivelens surfaces that are shaped to act together to form a correctiveophthalmic lens, the power of which varies according to the relativedisposition of the two lens elements, the method comprising the steps offorming a circular lens puck having two opposite faces, which are shapedin mutually corresponding central regions of each to form opposite lenssurfaces of one of the lens elements of the adjustable power lens, thepuck having at least one alignment feature, and thereafter edging thepuck to a desired eyeshape with reference to the alignment feature.

During the edging step, the lens puck is milled to the desired eyeshapefor a given frame; the puck is formed with a peripheral edge of thedesired eyeshape. For edging, a conventional lens edging maching may beused.

In some embodiments, the puck may have two or more separate alignmentfeatures. Upon edging the puck, at least one alignment feature mayremain within the eyeshape. In some embodiments, at least one alignmentfeature may be disposed outside the desired eyeshape such that it isremoved upon edging the puck.

By ‘alignment feature’ herein is meant a fiducial or other marking thatis applied to the puck or incorporated into the puck when it is made. Insome embodiments, the alignment feature(s) may be visible orsemi-visible markings of the kind known in the art. A semi-visualmarking may be particularly suitable for an alignment marking thatremains on the lens element after edging the puck.

Suitably the central region of one face of the puck may be formed with acubic or higher order lens surface such, for example, as a surfacedefined by formula (I) above, and an aligned central region of the otherface may be formed with a lens surface that is a regular surface ofrevolution. The regular surface of revolution may comprise asphero-cylindrical surface. Alternatively, the other face of one or bothlens elements may be formed with a multifocal or progressive lenssurface. Away from the central region of the puck, the one face maycomprise one or more peripheral regions where the cubic or higher orderlens surface is modulated to control the overall thickness of the puck,for example so it is suitable for moulding.

Suitably the puck may be made by injection moulding from a suitabletransparent thermoplastic material.

In some embodiments, the desired eyeshape may be non-circular. Thus, thepuck may be edged to form a lens element of circular or non-circularshape.

The puck may be edged to form the desired eyeshape having a peripheryand a plurality of tabs that protrude outwardly from the periphery.Alternatively, the tabs may be attached to the lens element afteredging.

Lens elements may be made in accordance with the fifth aspect of thepresent invention in matched pairs for subsequent assembly one behindthe other to form a variable optical power lens.

According to a sixth aspect of the present invention therefore there isprovided a method of making an adjustable optical power lens of the kindcomprising two lens elements that are slidable relative to one anotherin a direction transverse the optical axis and have respective lenssurfaces that are shaped to act together to form a corrective lens, thepower of which varies according to the relative disposition of the twolens elements, the method comprising forming two lens elements of thesame eyeshape in accordance with the method of the fifth aspect of thepresent invention, and thereafter assembling the two lens elements insuperposed relation such that they are slidable relative to one anotherin a direction transverse the optical axis and providing an opticalpower adjuster for controlling the relative disposition of the two lenselements.

In some embodiments, the lens made in accordance with the invention mayprovide a maximum power change of at least about +0.75 dioptres,preferably at least +2.0 dioptres, and more preferably at least +3.5dioptres.

Advantageously, each lens element may have at least one alignmentfeature within the eye shape as described above, the method comprisingaligning the lens elements with one another using the alignment featureswithin the eye shape

In a seventh aspect of the present invention there is provided a methodof making a pair of glasses which comprises making at least oneadjustable optical power lens in accordance with the sixth aspect of theinvention and assembling the at least one adjustable lens with a secondlens and one or more frame parts, including a nose-bridge and templearms, for mounting the glasses on a wearer's face. In some embodiments,the second lens may also be adjustable.

The present invention also comprehends a lens made in accordance withthe method of the sixth aspect of the invention and a pair of glassesmade in accordance with the method of the seventh aspect of theinvention.

Following is a description by way of example only with reference to theaccompanying drawings of embodiments of the present invention.

In the drawings:

FIG. 1 is a perspective view from the front, above and to one side of apair of glasses in accordance with the present invention comprising twovariable power lenses and showing a rectangular coordinate system ofmutually perpendicular axes x, y and z for defining parameters of eachlens, with the z-axis designated parallel to the optical axis of thelens.

FIG. 2 is a rear view of the glasses of FIG. 1.

FIG. 3 is a side view of the glasses, partly in cross-section on theline III-III of FIG. 2.

FIG. 4 is an enlarged view of a portion of FIG. 3, showing a left-handone of the variable power lenses, which comprises a stationary frontlens element, which is mounted in a detachable frame part, and aslidable rear lens element that are disposed one in front of the otheralong the z-axis of the lens.

FIG. 5 is a front view from above and to one side of the glasses of FIG.1 with the left-hand variable power lens exploded to show its componentparts.

FIG. 6 is a rear view from above and to one side of the glasses of FIG.1, corresponding to FIG. 5 and likewise showing the left-hand variablepower lens exploded.

FIG. 7 is a front view from below and to one side of the glasses of FIG.1 showing the detachable frame part that carries the front lens elementof the left-hand variable power lens detached and the rear lens elementexploded from a frame body to show protruding tabs on the rear lenselement for guiding movement of the rear lens element along the x-axisrelative to the frame body.

FIG. 8 is an enlarged view of a portion of FIG. 7, showing an upperinner tab on the rear lens element and a corresponding channel in theframe body with a leaf spring disposed therein for spring-loading therear lens element against .the frame body.

FIG. 9 is another enlarged view of a different portion of FIG. 7,showing an upper outer tab on the rear lens element and a correspondingchannel in the frame body, also with a spring fitted therein forspring-loading the rear lens element in the frame body.

FIG. 10 is another front view from below and to one side of the glassesof FIG. 1 showing the detachable frame part, which carries the frontlens element of the left-hand variable power lens, removed and the rearlens element fitted in the frame body to show the engagement of the tabsof the rear lens element in the corresponding channels in the frame bodyfor guiding movement of the rear lens element.

FIG. 11 is an enlarged view of a portion of FIG. 10, showing the upperinner tab on the rear lens element disposed in its correspondingchannel.

FIG. 12 is another enlarged view of a different portion of FIG. 10,showing the upper outer tab on the rear lens element disposed in itscorresponding channel in the frame body.

FIG. 13 is a side view of the glasses of FIG. 1 from above, with thefront lens element of the left-hand lens detached.

FIG. 14 is an enlarged view of a portion of FIG. 13 showing the upperouter tab on the rear lens element of the left-hand lens disposedslidably in its corresponding channel.

FIG. 15 is another side view of the glasses of FIG. 1 from above withthe front lens element of the left-hand lens detached, corresponding toFIG. 13, but with the rear lens element exploded from the frame body.

FIG. 16 is an enlarged view of a portion of FIG. 15 showing how theupper outer tab on the rear lens element of the left-hand lens and thecorresponding channel are configured.

FIG. 17 shows a circular puck for making a lens element in accordancewith the invention, showing the outlines of a plurality of differentlens elements of varying centrations that can be cut out from the puck.

FIG. 18 shows a circular puck for making a lens element in accordancewith the invention, showing the outlines of a plurality of differentlens elements of varying eyeshapes that can be cut out from the puck.

FIG. 1 shows a pair of glasses 1 in accordance with the presentinvention. The glasses 1 comprise two lenses 11, 12 and a plurality offrame parts for holding the lenses 11, 12 and for supporting the glasseson the face of a wearer (not shown) such that the lenses 11, 12 aredisposed in front of the wearer's eyes. The frame parts of the pair ofglasses 1 illustrated in FIG. 1 are conventional insofar as theycomprise two temple arms 13, 14 and a nose-bridge 15, which may befitted with nose-pads (not shown). The shapes of the lenses 11, 12,temple arms 13, 14 and nose-bridge 15 are not critical to the presentinvention and may be varied as desired. For instance, in someembodiments, the lenses 11, 12 may be integrated into a helmet orgoggles, or the frame parts may be connected to a head-band or the likefor retaining the lenses 11, 12 in front of the wearer's eyes. In thepresent embodiment, non-round lenses 11, 12 are employed.

Since they are designed to be worn by a person, the glasses 1 have anintrinsic orientation, having left and right sides, indicated by theletters L and R respectively in FIG. 1, a front and back, indicated bythe letters F and B, a top and bottom and, for each of the left andright sides of the glasses, inner and outer regions relative to thenose-bridge 15. It will be appreciated that the right and left templearms 13, 14 and right and left lenses 11, 12 have reflectional symmetrywith one another.

Each of the lenses 11, 12 is a variable optical power lens, as describedin more detail below. Whilst in the present embodiment, both lenses arevariable power lenses, in some other embodiments of the invention onlyone of the lenses may have variable power, while the other may have afixed optical power or even no optical power, depending on the intendedapplication or use for the glasses. For instance, a pair of glassescomprising a single variable power lens may be useful in post-eyesurgery situations where the optical power of one of a patient's eyesmay fluctuate during a period of recuperation. In the embodiment shown,the lenses 11, 12 are independently adjustable, but it is envisaged thatin some embodiments the lenses 11, 12 may be linked so they are adjustedtogether.

Each lens 11, 12 has an optical axis. A rectangular coordinate system ofmutually perpendicular axes x, y and z is a convenient way fordescribing parameters of the lens. The z-axis is designated parallel tothe optical axis, as shown in FIG. 1. The orientations of the x-axis andy-axis are explained in more detail below.

As best illustrated in FIG. 5, each variable power lens 11, 12 comprisestwo lens elements—a rear lens element 21 and a front lens element 22.The rear and front lens elements 21, 22 are arranged in tandem, with onebeing disposed behind the other as shown in FIGS. 4 and 5. The frontlens element 22 is optically clear, having front and rear faces 33, 34respectively, and is fixedly secured within a detachable frame partcomprising a peripheral surround 31 as described in more detail below.The rear lens element 21 is also optically clear, having front and rearfaces 40, 44 respectively and a plurality of protruding tabs 45-48. Thefront and rear lens elements 22, 21 may be free-formed from a suitablesynthetic thermoplastic resin material of suitably optical and physicalquality for ophthalmic use.

The rear lens element 21 is mounted slidably within a respective framebody 51 which is formed integrally with the nose-bridge 15. In theglasses 1 of the present embodiment therefore the frame body 51 of thetwo lenses 11, 12 are formed as a single piece including the nose-bridge15, but in different embodiments, the frame body 51 of each lens 11, 12may be formed separately and then joined to the nose-bridge 15. Further,in other embodiments (not shown) the front and rear lens elements 22, 21may both be mounted within a frame body, dispensing with the need for adetachable frame part such as surround 31.

As illustrated best in FIGS. 5 and 6, the rear lens element 21 isgenerally rectangular having upper and lower long side edges 41, 43 andinner and outer short side edges 49, 50. As will be seen from thefigures, the sides of the rear lens element 21 are not linear, but arecurved in a manner that is conventional for ophthalmic lenses. Thecorners between the long and short side edges are also rounded. The sideedges of the rear lens element 21 define its periphery.

Protruding from the periphery of the rear lens element 21 are an upperinner tab 45 which protrudes upwardly from the upper long side edge 41proximate the nose-bridge 15, inner and outer lower tabs 46, 47 whichdepend from the lower long side edge 43 and an upper outer tab 48 whichprotrudes outwardly from the outer side edge 50 of the rear lens element21 adjacent the upper side edge 41. As best shown in FIGS. 6, 14 and 15,the upper outer tab 48 is fabricated with a rack extension part 60having a rear surface 61, which is formed with a recess 62 therein thatdefines an upwardly facing bearing surface 64 as described in moredetail below, and an upper surface 65, which is formed with a pluralityof teeth 66 that form a rack for engagement with a pinion 70, alsodescribed in more detail below.

The frame body 51 has a front face 81 and a rear face 82 and defines ashape corresponding to the shape of the rear lens element 21 andcomprises upper and lower portions 52, 53 and inner and outer sideportions 54, 55. The height of the frame body 51 between the upper andlower portions 52, 53 is approximately the same as the height of therear lens element 21 between its upper and lower side edges 41, 43; thewidth of the frame body 51 between the inner and outer side portions 54,55 is wider than the width of the rear lens element 21 between its innerand outer side edges 49, 50 to allow the rear lens element 21 to slidefrom side to side relative to the frame body 51. The upper portion 52 ofthe frame body 51 is formed with an upwardly extending upper innerchannel 56 as best seen in FIGS. 8 and 11 for receiving the upper innertab 45 on the rear lens element 21. The upper inner channel 56 isdimensioned to allow the rear lens element 21 to slide relative to theframe body 51. The upper inner channel 56 accommodates a leaf spring 85as best seen in FIG. 8 which engages with the upper inner tab 45 on therear lens element 21 and pushes down on the same.

The lower portion 53 of the frame body 51 is formed with inner and outerlower channels 57, 58 as best seen in FIG. 5 for receiving the inner andouter lower tabs 46, 47 respectively. The inner and outer lower channels57, 58 are dimensioned to allow the tabs 46, 47 to slide therein. Thelower portion 53 of the frame body 51, the lower side edge 43 of therear lens element 21 and the inner and outer lower tabs 46, 47 areshaped, so that when the rear lens element 21 is fitted in the framebody, the lower side edge 43 of the rear lens element 21 is seated onthe lower portion 53 of the frame body 51, and the channels 57, 58 areconfigured to guide sliding movement of the rear lens element 21relative to the frame body 51.

The upper outer tab 48 of the rear lens element 21 is received in achannel 59 formed in the front face 81 of the frame body 51 in thecorner between the upper and outer portions 53, 55 (see FIG. 5). Withinthe channel 59, the front face 81 of the frame body 51 is formed with aforwardly protruding rib 83 which is formed with two slots for carryinga depending leaf spring 84. With the upper outer tab 48 of the rear lenselement 21 received in the upper outer channel 59, the rib 83 isreceived in the recess 62 formed in the rack extension part 60 forguiding sliding movement of the rear lens element 21 relative to theframe body 51 and the leaf spring 84 engages with and pushes downwardlyon the upwardly facing bearing surface 64 of the rack extension part 60.

The effect of the leaf springs 84, 85 pushing downwardly on the rearlens element 21 is to urge the rear lens element downwardly against thelower portion 53 of the frame body 51, so that its lower side edge 43 isfirmly seated against the lower portion 53 of the frame body 51, andthis serves to register the rear lens element 21 of the lens 12 to adatum to ensure accurate positioning of lens element 21 relative to theframe body 51. In the present embodiment, the slidable rear lens element21 is registered against a datum in the direction of the y-axis. It willbe understood that the principles of the invention may also be adaptedto spring-load the rear lens element 21 against the frame body 51 in thedirection of the z-axis as well as, or instead of, the y-axis.

The rear lens element 21 is thus able to slide from side to side withinthe frame body 51 in a direction transverse the optical axis and itsmovement is guided by the engagement of the tabs 45-48 in thecorresponding channels 56-59. The axis of movement of the rear lenselement 21 is designated the x-axis. As mentioned above, the z-axis isdesignated parallel to the optical axis of the lens 12. The y-axis isperpendicular to both the x- and z-axes and corresponds generally to thevertical axis relative to the normal orientation of the glasses 1 whenthey are worn. The leaf springs 84, 85 act to push against the rear lenselement 21 in the direction of the y-axis. In practice the rear lenselement 42 is curved as described in detail below, and accordingly thelocus of sliding movement defined by the tabs 45-48 and correspondingchannels 56-59 is also curved.

The teeth 66 of the rack extension portion 60 engage with the pinion 70which is mounted within a suitably shaped recess 71 formed in the rearface 82 of the frame body 51, as best seen in FIG. 6. The pinion 70 isfitted with a stub-axle 73 that is journaled in a hole 74 formed in theframe body 51 within the recess 71 to permit rotation of the pinion 70.The pinion 70 is also fitted with a thumbwheel 75 having a slightlygreater outer diameter than the pinion 70. As can be seen in FIG. 2, thethumbwheel 75 protrudes above the upper portion 52 of the frame body 51so that it can be engaged with a wearer's fingertip for manuallyrotating it. Rotation of the thumbwheel 75 causes corresponding rotationof the pinion 70 which, since it is engaged with the teeth 66 of therack extension portion 60 thus causes sideways movement of the rear lenselement 21 relative to the frame body 51. The thumbwheel 75 can thus beused by the wearer for adjusting the power of the lens 12 as describedin more detail below. As will be seen from the figures, each lens 11, 12has its own adjustment mechanism comprising a thumbwheel 75 forindependent adjustment of the two lenses 11, 12, but as mentioned above,in some embodiments, a single adjustment mechanism (not shown) may beprovided to adjust both lenses 11, 12 simultaneously.

As mentioned above, in the present embodiment, the front lens element 22is mounted fixedly within a detachable frame part comprising a lenssurround 31. The lens surround 31 has a front face 35 and a rear face36. The rear face 36 of the lens surround 31 comprises a skirt portion37 that extends around the upper, lower and outer portions of the lenssurround 31. The lens surround 31 is shaped and configured to mate withthe lens body 51 for removably attaching the lens surround 31 to thelens body 51. When attached, the skirt portion 37 extends over theupper, lower and outer side portions 52, 53, 55 of the lens body 51. Thelens surround 31 comprises an upper outer shoulder portion 38, whichextends over and closes the upper outer channel 59 formed in the framechassis 51 and the front of the hole 74 that accommodates the pinionaxle 73, and an upper inner shoulder portion 39 that is configured toabut a corresponding shaped step 17 formed between the nose-bridge 15and the frame body 51. The interengagement of the skirt portion 37 andinner and outer upper shoulder portions 38, 39 with correspondingformations on the frame chassis 51 serve to position the lens surround31 relative to the frame body 51. The frame surround 31 is dimensionedto form a close fit on the frame body 51 such that it is held in placeby friction. If desired, interengaging snap fittings or detents may beprovided on the lens surround 31 and frame body 51 for extra security.

In order to locate the front lens element 22 accurately relative to therear lens element 21, the rear face 36 of the lens surround 31 and thefront face 81 of the frame body 51 are formed with interengagingformations. In particular, the rear face 36 of the lens surround 31 andfront face 81 of the frame body 51 are formed with interengagingalignment pins 90 and corresponding recesses 92 in which the alignmentpins 90 are received. All of the alignment pins 90 may be formed oneither the lens surround 31 or frame body 51, or one or more alignmentpins 90 may be provided on the lens surround 31 and one or more on theframe chassis 51. In the present embodiment, two alignment pins 90 areprovided on the front face 81 of the frame body 51 and one alignment pin90 (not shown) is provided on the rear face 36 of the lens surround 31for engaging in the recess 92 shown in FIG. 5 in the inner portion 54 ofthe frame body 51. Regardless of whether the alignment pins 90 areprovided on the lens surround 31 or frame body 51, at least two, andpreferably three or more, alignment pins 90 should be provided.

The alignment pins 90 and recesses 92 thus serve accurately to locatethe front lens element 22 relative to the frame body 51 and thereforethe rear lens element 21. When attached to the frame body 51, the frontlens element 22 is mounted immovably relative to the rear lens element21. The removability of the surround 31 allows the front face 40 of therear lens element 21 and the rear face 34 of the front lens element 22to be accessed for cleaning. In some embodiments, at least the frontface 40 of the rear lens element 21 and the rear face 34 of the frontlens element 22 may be coated with a hydrophobic, super-hydrophobic oroleophobic coating of the kind known in the ophthalmic industry forprotecting the lens surfaces against dust and dirt. For example PTFE maybe used for this purpose.

In some embodiments, the detachable lens surround 31 may be omitted andthe front lens element 22 may be fitted immovably to the frame body 51in front of the movable rear lens element 21.

The front and rear lens elements 22, 21 form a variable optical powerlens 12. In order to achieve this, the thicknesses of the front and rearlens elements 22, 21 are controlled to provide cooperating lens surfacesthat give a different lens power depending on the relative dispositionsof the two lens elements 22, 21. In general, one face 33, 34; 40, 44 ofeach of the lens elements 22, 21 is formed with a cubic or higher ordersurface, while the other face 34, 33; 44, 40 of each lens element 22, 21is formed with a surface that is a regular surface of revolution, forexample sphero-cylindrical, or another conventional ophthalmic lenssurface, for example a multifocal or progressive lens surface. It may bedesirable for the two lens elements 22, 21 to define a base curve, withthe front face 33 of the front lens element 22 convex, and the rear face44 of the rear lens element 21 concave, so that as the lens 12 isadjusted by sliding the rear lens element 21 relative to the frame body51, or when the wearer moves his or her eye from side to side, thedistance between the eye and the lens 12 remains substantially constant.Specifically, the locus of sliding movement defined by the tabs 45-48and corresponding channels 56-59 may be concentric with the quadraticbase curve component of the lens thickness t as defined by the formulabelow.

In the present embodiment, the front face 40 of the rear lens element 21and the rear face 34 of the front lens element 22, as defined by thethickness t of the lens element 21, 22 parallel to the z-axis, are givencubic surfaces according to the formula:

$\begin{matrix}{t = {{A\left( {\frac{x^{3}}{3} + {xy}^{2}} \right)} + {Dx} + E}} & (I)\end{matrix}$

wherein D is a constant representing the coefficient of a prism removedto minimise lens thickness and may be zero, E is a constant representinglens element thickness at the optical axis, x, y and z are the axesdescribed above and A is a constant representing the rate of lens powervariation with relative lens element movement in the x direction, beingpositive for one of the lens elements 22, 21 and negative for the otherlens element 22, 21. Other suitable cubic and higher-order surfaces aredescribed in U.S. Pat. No. 3,305,294 (Alvarez), U.S. Pat. No. 3,583,790(Baker), U.S. Pat. No. 7,338,159 (Spivey), U.S. Pat. No. 7,717,552(Spivey), U.S. Pat. No. 5,644,374 (Mukaiyama) and WO 2013/030603 (GiciLabs), the contents of all of which are incorporated herein byreference.

The present invention is not limited by the precise form of the lenssurfaces used, only that the lens elements 22, 21 should cooperate toform a variable power lens, the power of which can be adjusted byrelative movement of the two lens elements 22, 21 in a directiontransverse the optical axis of the lens 11, 12 under the control of theadjustment mechanism 60, 70.

In accordance with one aspect of the present invention however it isimportant that the rear and front lens elements 21, 22 are configuredand arranged such that as the rear lens element 21 is moved inwardly onthe x-axis relative to the frame body 51, the optical power of the lens12 progressively increases. In other words, when the thumbwheel 75associated with the left-hand lens 12 of the glasses 1 is rotatedclockwise as viewed from behind (see FIG. 2) the rear lens element 21 ismoved inwardly towards the nose-bridge 15 to increase the power of thelens 12. When the rear lens element 21 is moved outwardly on the x-axisrelative to the frame body 51, the optical power of the lens 12 isdecreased. (For the right-hand lens 11, the associated thumbwheel 75should be rotated anticlockwise to move the rear lens element of thatlens inwardly to increase its power).

As mentioned above, in order to permit lateral sliding of the rear lenselement 21 of the lens 12 in the present embodiment of the invention,the width of the rear lens element 21 between its inner and outer sideedges 49, 50 is less than the width between the inner and outer portions54, 55 of the frame body 51. This is best seen in FIG. 2 in which aninner gap 101 can be seen between the inner side edge 49 of the rearlens element 21 and the inner portion 54 of the frame body 51, and anouter gap 102 is visible between the outer side edge 50 of the rear lenselement 42 and the outer portion 55 of the frame body 51. The sizes ofthe inner and outer gaps 101, 102 change as the rear lens element 21 ismoved from side to side under the control of the thumbwheel 75 and rackand pinion mechanism 60, 70. In accordance with the present embodiment,the size of the inner gap 101 should be minimised when the lens 12 is inits maximal power position, with the rear lens element 21 moved fullyinwardly towards the nose-bridge 15. This is because as the wearerincreases the power of the lens for viewing near objects, for examplecomputer screens or for reading, his or her eyes will naturally convergethereby reducing the interpupillary distance.

The inner and outer side edges 49, 50 of the rear lens element 21 willbe visible to the wearer in at least some positions of the rear lenselement 21, and it is desirable that these edges should not distract thewearer as far as that can be avoided. In the present embodiment, theperiphery of the front lens element 22 is concealed by the lens surround31. In accordance with the present invention, the difference in thewidths of the rear lens element 21 between its inner and outer sideedges 49, 50 and the front lens element 22 between the inner and outerside portions 54, 55 of the frame body 51, i.e. along the x-axis, shouldbe no more than about 8 mm, preferably less than 6 mm, and morepreferably less than 4 mm. In the maximum power position of the presentembodiment, the inner side edge 49 of the rear lens element 21 isaligned with the inner portion 54 of the frame body 51 so that the widthof the inner gap 101 is zero or as close to zero possible while thewidth of the outer gap 102 in this position is no more than about 8 mmand preferably less, as described above. In the minimal power position,the outer side edge 50 of the rear lens element 21 is aligned with theouter side portion 55 of the frame body 51 so that the width of theouter gap 102 is zero or as close to zero possible while the width ofthe outer gap 102 in this position is no more than about 8 mm andpreferably less, as described above.

It will be understood that in other embodiments, in the maximal powerposition, the outer side edge 50 of the rear lens element 21 may bealigned with the outer side portion 55 of the frame body. In still otherembodiments, in the minimal power position, the inner side edge 49 ofthe rear lens element 21 may be aligned with the inner side portion 54of the frame body 51. In these other embodiments, the frame body 51 maybe configured to conceal the inner side edge 49 of the rear lens element21 in the maximal power position and/or the outer side edge 50 of therear lens element 21 in the minimal power position, for instance byhaving a recess formed in the frame body 51 in which the side edge(s)49, 50 concerned are received and hidden from view.

The present invention also provides an improved method for manufacturingthe front and rear lens elements 22, 21 of the lens 12.

According to the invention, each of the front and rear lens elements 22,21 is first injection moulded in the form of a circular puck 200 ofnon-uniform thickness, as shown in FIGS. 17 and 18. The puck is formedwith two opposite faces 201, 202 and has a circular periphery 205. Oneof the faces 201 is formed, in a central region 204, with a cubic orhigher-order surface of the kind described in detail above that iscentred on the centre of the puck 200. For example, the one face 201 maybe formed with a surface described by formula (I) above. The other face202 is formed with a surface which is a regular surface of revolutionsuch, for example, as an ophthalmic sphero-cylindrical surfacecomprising a sphere and/or cylinder component. The regular surface ofrevolution formed on the other face 202 may be confined to the centralregion of the puck 200 in alignment with the central region 204 on theone face 201 on which the cubic or higher-order surface is formed. Insome embodiments, the other face 202 may be formed with a multifocal orprogressive lens surface. It will be appreciated that the shape of thelens surface formed on the one face 201 of the puck 200 is defined bythe thickness of the puck 200 between the two faces 201, 202 accordingto the selected cubic or higher order function.

Away from the central region 204 of the puck 200, towards its periphery205, the thickness of the puck would become very large in some regionsand very thin in other regions and potentially difficult or evenimpossible to make as result of the behaviour of the cubic orhigher-order function. Accordingly, in circumferentially spacedperipheral regions 206 towards its periphery 205, the puck 200 is formedwith an adjusted thickness that is greater or less than would otherwisebe implied by the cubic or higher-order function, and the cubic orhigher-order surface is “blended in” to those peripheral regions 206 ofmodulated thickness.

After being released from the mould, the circular puck 200 is markedwith one or more fiducial markings F1, F2 as alignment features on oneor both surfaces 201, 202 to locate accurately the position of the cubicor higher-order surface relative to the physical geometry of the puck200 and optionally for alignment of the front and rear lens elements asdescribed in more detail below.

Thereafter, the puck 200 can be edged to form a non-circular lenselement 22, 21 of a desired shape with a required centration. As long asthe position of the cubic or higher-order surface relative to the puck200 is identified by the fiducial marking(s) F1, F2, the circular puck200 can be held by a suitable tool and edged by trimming its peripheryto the desired shape with the required centration. FIG. 17 shows thepositions of lenses c1, c2, c3 of the same eyeshape but differentcentres, while FIG. 18 shows the positions of lenses of differenteyeshapes s1, s2, s3, which can all be cut out from the same puck 200.The blended in peripheral regions 206 do not fall within the final lenselements 32, 42. It will be observed that while the fiducial markings F1fall outside the eyeshapes and so are removed on edging the puck 200,while the fiducial markings F2 fall inside the eyeshapes and are notremoved. The fiducial markings F2 may be visible or semi-visiblemarkings of the kind known in the art.

One or both surfaces 201, 202 of the puck 200 can then be treated, ifdesired, with one or more optical coatings of the kind known in the art,including, for example, a hydrophobic, super-hydrophobic or oleophobiccoating as described above.

The lens elements 22, 21 should be manufactured in matching pairs of thesame eye shape and centration for assembly to form a variable opticalpower lens 11, 12 of the kind described above by assembling the lenselements 22, 21 one behind the other such that they are slidablerelative to one another in a direction transverse the optical z-axis andproviding a suitable adjustment mechanism (60, 70) for controlling therelative disposition of the two lens elements. The fiducial markings F2that remain within the eyeshape after edging the puck 200 may be usedfor correctly aligning the front and rear lens elements 22, 21 with eachother in the frame.

One or both lens elements 22, 21—for instance a rear lens element 21 ofthe kind described above—may be cut out from the puck 200 with outwardlyprotruding peripheral tabs 45-48. Alternatively, peripheral tabs 45-48may be attached to the lens element 21 after it has been cut out fromthe puck 200, for example by bonding or welding. Depending on theprecise form of the cubic or higher-order function used to define thelens surface, the lens produced in accordance with the method of thepresent invention may provide a variation in optical power of at least+0.75 dioptres and, in some embodiments, up to +2.0 dioptres or +3.5dioptres.

The advantage of the method of making a lens 11, 12 with lens element22, 21 according to the present invention is that it allows lenselements of multiple different eye shapes and centrations to be formedfrom the same shaped puck 200. This greatly simplifies the manufactureof the lens elements and allows a stock of pucks 200 to be made and thenfinished by edging to order.

1. A method of fabricating a lens element for an adjustable power lensof the kind comprising two lens elements that are slidable relative toone other in a direction transverse the optical axis of the lens andhave respective lens surfaces that are shaped to act together to form acorrective lens, the power of which varies according to the relativedisposition of the two lens elements, the method comprising the steps offorming a circular lens puck having two opposite faces, which are shapedto form opposite lens surfaces of one of the lens elements of theadjustable power lens, one face of the lens puck being formed with acubic or higher order lens surface, and the lens puck having at leastone alignment feature that locates the position of the cubic or higherorder surface relative to the physical geometry of the lens puck, andthereafter edging the lens puck to a desired eye shape with reference tothe alignment feature.
 2. A method as claimed in claim 1, wherein thelens puck has two or more separate alignment features.
 3. A method asclaimed in claim 2, wherein upon edging the lens puck at least one ofthe alignment features remains within the desired eye shape.
 4. A methodas claimed in claim 3, wherein said at least one alignment feature thatremains within the desired eye shape is visible or semi-visible.
 5. Amethod as claimed in claim 2, wherein upon edging the lens puck, atleast one of the alignment features is disposed outside the desired eyeshape and is removed.
 6. A method as claimed in claim 1, wherein thelens puck is formed by injection moulding.
 7. A method as claimed inclaim 1, wherein the lens puck is edged to a non-circular eye shape. 8.A method as claimed in claim 1, wherein the lens puck is edged to an eyeshape having a periphery and a plurality of tabs that protrude outwardlyfrom the periphery.
 9. (canceled)
 10. A method as claimed in claim 1,wherein the other face of the lens puck has a surface which is a regularsurface of revolution.
 11. A method as claimed in claim 10, wherein thelens puck has a surface which is a sphero-cylindrical lens surface, amulti-focal lens surface, or a progressive lens surface.
 12. A method ofmaking an adjustable optical power lens of the kind comprising two lenselements that are slidable relative to one other in a directiontransverse the optical axis of the lens and have respective lenssurfaces that are shaped to act together to form a corrective lens, thepower of which varies according to the relative disposition of the twolens elements, the method comprising: forming two lens elements of thesame shape in accordance with the method of claim 1, thereafterassembling the two lens elements in superposed relation such that theyare slidable relative to one another, and providing an optical poweradjuster for controlling the relative disposition of the two lenselements.
 13. A method of making an adjustable optical power lensaccording to claim 12, wherein the lens has a maximum power change of+3.5 dioptres.
 14. A method of making an adjustable optical power lensaccording to claim 12, wherein each lens element has at least onealignment feature within the desired eye shape, the method comprisingaligning the lens elements with one another using the alignment featureswithin the desired eye shape.
 15. A method of making a pair of glasseswhich comprises: making at least one adjustable optical power lens inaccordance with claim 12, and assembling the at least one adjustablelens with a second lens and one or more frame parts, including a bridgeand temple arms, for mounting the glasses on a user's face.
 16. A lensmade in accordance with the method of claim
 12. 17. A pair of glassesmade in accordance with the method of claim
 15. 18-46. (canceled)